Scapulothoracic muscle activity during kinetic chain variations of a prone elevation exercise.

BACKGROUND: Scapular rehabilitation exercises should target appropriate muscles. Recently, adding external rotation resistance to scapular exercises has gained interest. Moreover, clinical experts advise kinetic chain integration into shoulder rehabilitation exercises. OBJECTIVE: To investigate scapular muscle activity during kinetic chain variations of a prone elevation exercise. METHODS: Activity of the upper (UT), middle (MT), and lower (LT) trapezius and serratus anterior (SA) muscles was determined with surface electromyography (EMG) in 31 asymptomatic participants during six prone elevation exercise variations. Variation was created by adding external rotation resistance, adding trunk extension, or changing exercise position (prone on a Swiss ball with knees or feet supported, or prone on a physiotable). All data were normalized as a percentage of maximal voluntary isometric contraction (% MVIC). For each muscle, a Friedman's ANOVA was conducted to analyse statistical differences in EMG signal intensity between exercises. RESULTS: The LT was moderately (42 - 48% MVIC) and MT highly (63 - 66% MVIC) activated during all exercise variations. No significant differences between exercises for these muscles could be detected. Adding external rotation to a prone elevation exercise decreased UT activity while adding trunk extension increased UT activity. Altering exercise position had no influence on scapular muscle activity except increased UT activity when lying prone on a physiotable with trunk extension. CONCLUSION: Prone elevation exercises are appropriate for facilitating LT and MT activity. Adding external rotation inhibits UT activity while UT facilitation could be achieved when adding trunk extension.

Quantifying acromiohumeral distance in elite male field hockey players compared to a non-athletic population.

BACKGROUND: Shoulders of elite field hockey players are loaded continuously during play. Frequent high shoulder loading is known to influence certain shoulder variables, such as acromiohumeral distance. However, the influence of elite field hockey play on acromiohumeral distance is not examined yet. OBJECTIVE: To examine the acromiohumeral distance in elite male field hockey players compared to a non-athletic control group. DESIGN: Cross-sectional study. METHODS: Fifty male participants were included; 25 elite field hockey players (age: 24.0±2.72 years; weight: 77.2±5.29kg; height; 180.5±5.37cm) and 25 age- and gender matched non-athletes (23.0±2.29 years; weight: 75.7±9.53kg; height: 181.8±5.52cm). A Telemed-Colormaster-128 EXT-IZ device was used to bilaterally obtain ultrasound acromiohumeral distance images at 3 different angles of shoulder abduction in the frontal plane. RESULTS: Field hockey players showed a bilateral larger acromiohumeral distance at 45° (mean difference: 1.46mm [95% CI 0.46; 2.46]; p=0.005) and 60° (mean difference: 1.07mm [95% CI 0.21; 1.93]; p=0.016) compared to controls. In both groups, a significant but clinically less relevant, side difference was established for the acromiohumeral distance at 60° (mean difference: 0.79mm [95% CI 0.21; 1.34]; p=0.009). CONCLUSION: With active shoulder abduction, elite field hockey players show a larger acromiohumeral distance in comparison to non-athletic participants. This may be a protective sport-specific adaptation, to better guard the shoulder from injury. Thus, acromiohumeral distance measurement may help physical therapists/coaches decide which athletes could benefit from specific, additional exercises aimed at enlarging the subacromial space.